linux-kernel - Re: [PATCH 2/4 v3] drm: Introduce drm_connector_register

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Message-ID: <CANq1E4QSaEOM8Ug_KxCO1unqY_iEP+WOttx=9xHH1oNWd-X2Mg@mail.gmail.com>
Date:	Wed, 23 Mar 2016 12:13:24 +0100
From:	David Herrmann <dh.herrmann@...il.com>
To:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Daniel Vetter <daniel@...ll.ch>,
	David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH 2/4 v3] drm: Introduce drm_connector_register_all() helper

Hi

On Wed, Mar 23, 2016 at 9:42 AM, Alexey Brodkin
<Alexey.Brodkin@...opsys.com> wrote:
> As a pair to already existing drm_connector_unregister_all() we're adding
> generic implementation of what is already done in some drivers.
>
> Once this helper is implemented we'll be ready to switch existing
> driver-specific implementations with the generic one.
>
> Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: David Airlie <airlied@...ux.ie>
> ---
>
> Changes v2 -> v3:
>  * Updated title with capital after colon
>  * Simplified failure path with direct and unconditional invocation of
>    unregister_all()
>  * Updated kerneldoc description of the drm_connector_register_all()
>
> Changes v1 -> v2:
>  * Rename drm_connector_unplug_all() to drm_connector_unregister_all()
>  * Use drm_for_each_connector() instead of list_for_each_entry()
>  * Updated kerneldoc for drm_dev_register()
>
>  drivers/gpu/drm/drm_crtc.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_drv.c  |  6 +++++-
>  include/drm/drm_crtc.h     |  3 ++-
>  3 files changed, 50 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 65488a6..21eea11 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -1081,6 +1081,49 @@ void drm_connector_unregister(struct drm_connector *connector)
>  EXPORT_SYMBOL(drm_connector_unregister);
>
>  /**
> + * drm_connector_register_all - register all connectors
> + * @dev: drm device
> + *
> + * This function registers all connectors in sysfs and other places so that
> + * userspace can start to access them. Drivers can call it after calling
> + * drm_dev_register() to complete the device registration, if they don't call
> + * drm_connector_register() on each connector individually.
> + *
> + * When a device is unplugged and should be removed from userspace access,
> + * call drm_connector_unregister_all(), which is the inverse of this
> + * function.
> + *
> + * Returns:
> + * Zero on success, error code on failure.
> + */
> +int drm_connector_register_all(struct drm_device *dev)
> +{
> +       struct drm_connector *connector;
> +       int ret;
> +
> +       mutex_lock(&dev->mode_config.mutex);
> +
> +       drm_for_each_connector(connector, dev) {
> +               ret = drm_connector_register(connector);
> +               if (ret) {
> +                       /*
> +                        * We may safely call unregister_all() here within
> +                        * area locked with mutex because unregister_all()
> +                        * doesn't use locks inside (see a comment in that
> +                        * function).
> +                        */

Ugh? unregister_all() says:

/* FIXME: taking the mode config mutex ends up in a clash with sysfs */

This strongly contradicts your comment. Anyway, regardless how you
want to fix it: You better unlock the mode-config mutex before
returning below.

Thanks
David

> +                       drm_connector_unregister_all(dev);
> +                       return ret;
> +               }
> +       }
> +
> +       mutex_unlock(&dev->mode_config.mutex);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL(drm_connector_register_all);
> +
> +/**
>   * drm_connector_unregister_all - unregister connector userspace interfaces
>   * @dev: drm device
>   *
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 167c8d3..2c9a2b6 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -715,7 +715,11 @@ EXPORT_SYMBOL(drm_dev_unref);
>   *
>   * Register the DRM device @dev with the system, advertise device to user-space
>   * and start normal device operation. @dev must be allocated via drm_dev_alloc()
> - * previously.
> + * previously. Right after drm_dev_register() the driver should call
> + * drm_connector_register_all() to register all connectors in sysfs. This is
> + * a separate call for backward compatibility with drivers still using
> + * the deprecated ->load() callback, where connectors are registered from within
> + * the ->load() callback.
>   *
>   * Never call this twice on any device!
>   *
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 42d9f4d..6a34117 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -2214,7 +2214,8 @@ void drm_connector_unregister(struct drm_connector *connector);
>
>  extern void drm_connector_cleanup(struct drm_connector *connector);
>  extern unsigned int drm_connector_index(struct drm_connector *connector);
> -/* helper to unregister all connectors from sysfs for device */
> +/* helpers to {un}register all connectors from sysfs for device */
> +extern int drm_connector_register_all(struct drm_device *dev);
>  extern void drm_connector_unregister_all(struct drm_device *dev);
>
>  extern int drm_bridge_add(struct drm_bridge *bridge);
> --
> 2.5.0
>